Safety system responsive to temperature and fluid flow



Dec. 31, 1940. R A wn- 2,227,291

SAFETY SYSTEM RESPONSIVE TO TEMPERATURE AND FLUID FLOW Filed May 26,1938 Patented Dec. 31, 1940 PATENT OFFICE SAFETY SYSTEM RESPONSIVE TTEM- PERATURE AND FLUID FLOW Robert A.. Wittmann, Chicago, Ill.,assignor to Chicago By-Products Corporation, a corporation of IllinoisApplication May 26, 1938, Serial No. 210,144

4 Claims.

My invention relates, generally, to safety sys tems for gas burners ofthe type disclosed in my Patent No. 2,185,490, and it has particularrelation to systems of this nature in which controls are provided thatare responsive to both temperature and fluid flow.

In devices for the automatic fuel control to heating apparatus employinga fan or blower to force or draw air over the heating sections or heattransfer surface, it is desirable and often necessary to be assured thatthe air is passing over the heating surfaces before the main burner isput into operation. At the same time itis also necessary to be assuredthat fuel cannot be fed 5 to the main burner unless the pilot flame orother ignition means is either burning or in satisfactory operativecondition.

An important object of my invention is to provide for checking as towhether or not the pilot 20 is burning at each time that there is ademand or call for heat.

Another important object of my invention is to prevent the main burnerof a heating system from going into operation unless air is passing 25over the heating or heat transfer sections to which heat is applied fromthe flame of the main burner.

A further object of my invention is to provide a simple form of safetypilot system employing principally a strip of metal and therebyeliminating the usual moving parts that are complicated by linkages andleverages, electric contacts, bleed valves, and other sources of likelycauses of trouble.

Still another object of my invention is to provide a safety pilotcontrol system which, when the pilot burner is lighted, will go intooperation in a predetermined time, preferably in about thirty seconds,so as to give the operator ample 40 time to move away from the furnacebefore the main humer is lighted and which will shut down or cause toshut down the main burner quickly in case that the pilot burner isextinguished. Samples of my control system capable of effect- 45 ing theforegoing objects have been operated successfully and consistently forshutting down 1 the main burner within approximately three seconds afterthe exting uishment of the pilot burner, even with-the main burner on.

A further object of my invention is to provide a safety pilot systemwhich does not require any adjustments, thereby eliminating tampering byunauthorized or inexperienced persons.

Other objects of my invention will, in part, be 66 obvious and in partappear hereinafter.

Accordingly, my invention is disclosed in the embodiment thereof shownin the accompanying drawing and it comprises the features ofconstruction, combination of parts, and arrangement of elements whichwill be exemplified in the con- 5 struction hereinafter set forth andthe scope of the application of which will be indicated in the appendedclaims.

For a more complete understanding of the nature and scope of myinvention reference may 10 be had to the following detailed descriptiontaken in conjunction with the accompanying drawing in which the singlefigure illustrates a concrete embodiment of my invention.

Referring now particularly to the drawing, it will be observed that thereference character In designates, generally, a gas heated hot airfurnace. The furnace in may be a conventional coal fired hot air furnacewith its grates removed and a main gas burner H installed, as is thepractice in changing from burning coal to gas.

A fan i2 is located in the cold air return i3 for drawing in cold airand forcing it over the heating surface it of the furnace Ill and outthrough the hot air pipes IS. The fan I2 is driven by a suitable motorit which may be connected by means of conductors l1 and I8 to theenergized conductors i9 and 20. For example, the conductors l9 and 20may be connected to a source of 110 volt alternating current. A switch2| is provided in conductor I8 for controlling the operation of themotor It as desired.

The main gas burner H in the fire box of furnace Ill, may be connectedby a pipe 25 to a gas supply main 26 through a shut-off valve shown,generally, at 21. The shut-off valve 21 comprises a valve port 28 whichmay be closed by a valve body 29 that is operated by an electromagnet30. For purposes of illustration the valve body 29 is shown as beinglifted off of the valve port 28. It will be understood, however, thatwhen the eiectromagnet 30 is deenergized, the valve body 29 will dropand close the valve port 28, thereby preventing the flow of gas throughthe shut-off valve 21.

With a view to lighting the main gas burner II a pilot burner 3| isprovided that is connected by a suitable pipe 32 to the supply main 26.It will be understood that, under normal operating conditions, the pilotburner 3| is lighted continually.

The electromagnetsli may be energized from the energized conductors Hand20. One terminal of electromagnet 30 is directly connected to theenergized conductor 20 through a conductor 33. The other terminal isindirectly connected to the energized conductor l9 through a conductor34, containing in series a mercury control switch 35, and conductor l8through switch 2|. Thus the electromagnet 30 can not be energized untilboth the mercury control switch 35 and switch 2| are closed.

The conductor |1, connecting one terminal of the motor 5 to theenergized conductor 20, contains in series a thermostatic switch 40.This thermostatic switch 40 may be any one of several different typesand might be located in a position to be responsive to the temperatureof a room heated by the furnace I0. When the room gets to apredetermined temperature the contact at 4| will open and the motor i6driving the fan l2 will be turned off. It is also seen that when theroom cools sufficiently the contact at 4| will be closed and the fan I2started, thereby again forcing air through the furnace ill to heat theroom.

When the fan |2 is stopped and not forcing air over the heating surfaceH the main burner II should be turned off for two reasons. First, if airis not passing over the heating surface l4 when the main burner II isheating it, it may become overheated and may be seriously damaged by thehigh temperature to which it will be raised. Secondly, when the fan i2is not running, the rooms heated by furnace II) are warm enough and theheat from the main burner II is not needed.

With a view to causing the main burner H to be put in operation onlywhen the fan I! is running, a control mechanism shown, generally, at 42is provided. The control mechanism 42 operates the mercury controlswitch 35 which has been shown to be connected in series relationshipwith electromagnet 30. This mercury control switch 35 may be of the typehaving a pool of mercury 43 which is moved from one end to the other ofthe switch in accordance with tilting thereof. The control switch 35 ismounted for operation on a suitable operating member or shaft 44.

The control mechanism 42, besides controlling the operation of the maingas burner II, also performs the safety measure of not allowing theshut-off valve 21 to open unless the pilot 3| is burning. It is seenthat this is very important, as it would be extremely dangerous to havegas escaping unignited through the main burner II.

In order to operate the switch 35 in accordance with whether or not thepilot 3| is burning, an arm 45 is provided extending downwardly fromshaft 44 and having at its lower end a permanent magnet 46, having ahorseshoe shape. Cooperating with the permanent magnet 46 is a member 41of Curie point metal, in the shape of an angle. The vertical leg ofmember 41 is arranged to bridge between the ends of the permanent magnet46 and the horizontal leg is positioned in thermally conductive relationto the flame of the pilot burner 28. When this flame is absent, thetemperature of the member 41 is below the Curie point and possessesmagnetic properties. When the pilot burner 3| is lighted and the member41 is heated above its Curie point, it loses its magnetic properties tosuch an extent that it functions as if it were made of non-magneticmaterial.

When the pilot burner 3| is not lighted, the member 41 of Curie pointmetal possesses magnetic properties. Since the member 41 is stationarilymounted, the permanent magnet 46 is attracted and held in contact withthe member 41 and, since the permanent magnet 46 is mechanicallyconnected to the shaft 44 carrying the switch 35, the latter is held inthe position illustrated in the drawing, which is the open circuitposition. As long as the pilot burner 3| remains unlighted, thepermanent magnet 46 will hold itself in engagement with the member 41 ofCurie point metal and thereby will hold the switch 36. controlling theelectromagnet 36, in the open position. When the pilot burner 3| islighted, the member 41 of Curie point metal will be heated and will loseits magnetic properties and the permanent magnet 46 will no longer clingto it. However, the rotating force due to the weight of the permanentmagnet 46 is so counterbalanced by the adjustable weight 43, that whenthe member 41 is heated and therefore the permanent magnet 46 is notattracted to it, the shaft 44 will rotate slightly so that permanentmagnet 46 no longer engages member 41. It will, however, not rotatesuiiiciently to tilt the switch 36 enough to close it. This may becalled the intermediate position of the permanent magnet 46. As theresult, switch 35 will still remain in the open position until someoutside force is applied to the shaft 44 for rotating it sufllciently toclose it.

This outside force is supplied by the draft from the fan I2. For thispurpose the shaft 44 has extending upwardly therefrom an arm 46 whichcarries at its upper end a sail member 60. As illustrated, the sailmember 60 is positioned in the path of the air from fan II. This blastof air from the fan I! is sufficient to cause the sail member 50 to moveand rotate the shaft 44 for operating the control switch 35 to theclosed position, provided that the pilot burner 3| is lighted and thepermanent magnet 46 is not attracted to the member 41 of Curie pointmetal.

With a view to describing the operation of my safety system responsiveto temperature and fluid flow, assume that the pilot burner 3| islighted, the main burner II is out, and that the fan I2 is stopped.Under these conditions the permanent magnet 46 will not be attracted tothe member 41 and under the effect of gravity it will move to theintermediate position not touching the member 41. As there is no draftof air from the fan l2 the control switch 35 will be in the openposition, thereby, causing the electromagnet 30 to be deenergized. Nowif the room in which the thermostatic switch 46 is positioned coolssufficiently, the contact at 4| will be closed on the action of thethermostatic switch 4|! and the fan l2 will be started. When the fan I!starts the sail member 50 will be acted on by the draft set up andthereby cause the control switch 36 to'close. When the control switch 35closes the electromagnet 30 will become energized and gas will flow tothe main gas burner II and will be lighted by the pilot burner 3|. Afterthe room is heated sufficiently, the thermostatic switch 46 will openthe contact at 4| and cause the fan If to stop. When the fan I! stopsthere will no longer be a draft against the sail member 50 andconsequently the control switch 35 will open, thereby deenergizing theelectromagnet 30 and shutting off the gas supply to the main gas burnerII.

It will be seen, from the description of the operation given above, thatif the pilot burner 3| should go out for some reason and the fan I!should be started by the closing of the contact at 4|, the switch 36would not be closed as the permanent magnet 46 would cling to the member41 and as a result no gas would flow to the main burner I. But, sincethe air forced through furnace ID by the fan I2 is not heated thethermostatic switch 40 will not open the contact at 4| and the fan l2will continue running indefinitely. In order to prevent an occurrence ofthis nature, a bell or other alarm 55 may be connected to the conductorI I by the conductor 56 as shown. The other terminal is connected toconductor i8 by the conductor 51 through the switch 58. As shown, onecontact member of the switch 58 is carried on a projection of thedownwardly projecting member. The switch 55 is so set up that it willnot be closed unless the permanent magnet 46 is clinging to the member41 or Curie point metal as shown in the drawing. Now, it will be seenthat if the pilot burner 3| should go out the switch 58 will close andthe bell 55 will give warning of the condition.

It is to be understood that the alarm 55 and the corresponding contacts58 may optionally be omitted. In that event, the movable systemincluding magnet 46 need not shift to the intermediate positionheretofore described. That is to say, when the Curie point material 41loses its magnetic properties the magnet 46 need not move away, eventhough no attraction between the parts 55 and 1 exists. When thisattraction ceases, the draft acting on the sail is free to shift themovable system to the desired position of closing the switch 35 orperforming any other desired operation. Thus, when the alarm is notincorporated, the permanent magnet 45 may engage the member 41 at alltimes except when it is forced away by a draft acting against the sailmember 50.

Since certain further changes may be made in the foregoing constructionand different embodiments of the invention made without departing fromthe scope thereof, it is intended that all matter shown in theaccompanying drawing or described hereinbefore shall be interpreted asillustrative and not in a limiting sense.

I claim as my invention:

1. Safety control means responsive to temperature and fluid flowcomprising, in combination, a control switch, magnetic means operativelyconnected to said control switch, a body of Curie point material, andsail means operatively connected to said control switch, said magneticmeans being attracted to said body of Curie point material when saidbody is below its Curie point, there being substantially no attractionbetween said magnetic means and said body of Curie point material whensaid body is at a temperature above its Curie point.

2. Control means responsive to temperature and fluid flow comprising, incombination, a control switch, relatively movable cooperating magneticmeans and Curie point metal means, one of said means being'operativelyconnected to said control switch for controlling its operation accordingto whether the temperature of said Curie point metal means is above orbelow its Curie point, and fluid flow responsive means also operativelyconnected to said control switch and adapted to control its operation inaccordance with change in fluid flow.

3. Control means responsive to temperature and fluid flow comprising, incombination, a rockable member, switch means operated from one position"to another by said rockable member, relatively movable cooperatingmagnetic means and Curie point metal means, one of said means beingoperatively connected to said rockable member for moving it from oneposition to another according to whether the temperature of said Curiepoint metal means is above or below its Curie point, and fluid flowresponsive means also operatively connected to said rockable member formoving it from one position to another in accordance with change influid flow, said switch means being operable from one position toanother only under predetermined conditions of both temperature andfluid flow.

4. Control means responsive to temperature and fluid flow comprising, incombination, switch means carried on a rockable shaft, a permanentmagnet carried by said shaft, a body of Curie point metal in cooperativerelation to said magnet for controlling the position of said shaftaccording to whether the temperature of said Cin'ie point metal is aboveor below its Curie point, and a sail carried by said shaft forcontrolling its position in accordance with change in fluid flow, saidswitch means being operable from one position to another only underpredetermined conditions of bothtemperature and fluid flow.

ROBERT A. WI'I'IMANN.

